How good does a book about depression have to be before the reader becomes too depressed to read it? The further I got with Sally Brampton's utterly involving memoir, the harder it was to turn the pages. By the end of it, I was mightily relieved: the author had survived and so had I.

In her happy heyday, Brampton was the founding editor of Elle and a paragon of progressive women's journalism. She lived the aspirations of her readership, the archetypal juggler of catwalk afternoons and warm domesticity with husband and daughter. She also wrote novels, and even during her less successful launch of Red magazine you wouldn't have figured her as a candidate for mental institutions and the morbid confessional. She looked too spunky and too resilient and, absurd as it sounds, too attractive: her byline photograph showed cropped blonde hair, a childlike snub nose and a wide smile.

But there she was for almost four years, in and out of institutions, on and off the pills, sobbing to her friends on the phone that she was worthless. For a while, vodka and red wine seemed the answer; later, there were more desperate measures.

What switched this on? A divorce. A house move. A tough work stretch. A thyroid problem. The turn of the millennium. And perhaps none of the above. Her mood swung down at the start of 2000, but it took her a year of darkening confusion to seek help. Initially, she made vague attempts to take the advice of well-meaning friends to pull herself together, to be grateful for all the privilege and opportunity in her life. She found that each stab at normality brought with it only more profound depression, where 'every contemptuous glance, every irritated sigh from family and friends' drove her 'still further into the cold, black night'.

She writes of her despair with such fluidity and lyricism that it is sometimes difficult to imagine her as the stumbling and empty figure she describes, clinging on to walls lest the 'throat monster' gets her, unable to prepare a proper meal or sign a cheque, walking around London in dark glasses to conceal her tears.

She has 'suicidal ideation' for months, but her two attempts, both by overdose, appear quite late in the book and are described as almost incidental, a final marker of anguish, when even the life of her daughter is not enough to keep her afloat. 'It's the worst death,' a friend in hospital tells her of her own attempt with 400 paracetamol. 'It takes weeks, and then your liver packs up.' Brampton underdosed and her failures are marked by anger. Her distrust of the healing power of drugs is so sure that at one point, she ignores strict professional advice and jettisons all her medication in one go.

She has been criticised, unfairly I think, for commenting on her therapist's dress sense - an unusual choice of shawl, perhaps - as if she could never divorce her sense of gloom from her sense of style. But depression lumps everything in, heightening some observations as it dulls others, and Brampton's account is at its best when it roots itself in the everyday. This is her message: out of the sky comes unexpected universal disaster and it will smother the successful and the outwardly buoyant without discrimination.

Her story comes at a busy time for popular accounts of depression and derangement; it is almost a phenomenon for writers to compete with Dan Brown spinoffs and abused childhood miseries. As Brampton's publisher claims brazenly on the jacket of the book's proof copy, 'there is a huge niche market' for this kind of thing. Unfortunately, it seems to be getting bigger: the World Health Organisation has forecast that by 2020, depression will be the leading health challenge in the developing world.

How can they possibly know? And why the recent publishing rush? It may be that we are more willing to admit to what was once regarded as the last taboo, alongside those other last taboos of prostate cancer and sexually transmitted diseases. Depression can seem less of a hidden burden these days and more of a communal affliction - a GP's caseload is dominated by the illness, while the drug companies grow fat on discovering new anxieties for their panaceas. Brampton's stated aim is modest and clear, to hint at what may help, to offer hope of recovery and to connect with fellow depressives. She has already had some success: she writes that after her account of a suicide bid appeared in the Daily Telegraph in 2003, she received about 2,000 letters.

In Shoot the Damn Dog, the title a reference to the depressive 'black dog' days logged by Winston Churchill, Brampton attempts the difficult trick of fusing the personal with the general. Her writing is accessible, occasionally to the point of hokey clumsiness ('It's no picnic, a psychiatric ward'). But her story is compelling and unflinching and she makes no claims that her descent and slow recovery will match those of others. She is on less firm ground with her fleeting analysis of current scientific understanding of the disease, a conclusion she comically reaches herself: 'In my entirely subjective research into what makes happiness, or freedom from depression, I'd say that the single most effective habit is an open and receptive mind.'

She is supported throughout her ordeal by two friends, journalist Sarah Spankie, and a fellow depressive, Nigel Langford, to whom she jointly dedicates her book. With Langford, she shares gallows humour, while Spankie gets the calls at all hours and provides the reassuring breeze of the outside world (Brampton is strong on the notion that the clinically depressed will only benefit from visits by close friends, no matter how much one believes that solitude may be beneficial).

A third friend called Tom offers her a more volatile relationship and passionate sex. But he has children from an imploding marriage and a custody battle. They could not be together and they could not stay away, fleeting joy merging with desolation, and it ended in Brampton striking him. Or almost ended: the reader learns that after three years of distance, they recently reunited and wed, leaving Brampton in what she calls, 'in its own particular way, bliss'.

The qualifying phrase is a vital one, as if she doesn't quite trust her happiness or believe it will last. Depression, like addiction, and like wild love perhaps, is not a disease to be cured. It is managed and contained, in Brampton's case by brisk walks, the trust of friends, gardening, transcendental meditation, yoga, acupuncture and cognitive behavioural therapy (though it took her a while to value this). She is already blessed with a skill for communication. 'Sometimes, I wish I was in a full bodycast,' a fellow depressive tells her, 'with every bone in my body broken. Then maybe people would stop minimising my illness because they can actually see what's wrong with me. They seem to need physical evidence.' Sally Brampton's memoir provides further valuable proof.